Version 4.2.0

src/Asymp.cpp

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+/***************************************************/
+/*! \class Asymp
+    \brief STK asymptotic curve envelope class
+
+    This class implements a simple envelope generator
+    which asymptotically approaches a target value.
+    The algorithm used is of the form:
+
+    x[n] = a x[n-1] + (1-a) target,
+
+    where a = exp(-T/tau), T is the sample period, and
+    tau is a time constant.  The user can set the time
+    constant (default value = 0.3) and target value.
+    Theoretically, this recursion never reaches its
+    target, though the calculations in this class are
+    stopped when the current value gets within a small
+    threshold value of the target (at which time the
+    current value is set to the target).  It responds
+    to \e keyOn and \e keyOff messages by ramping to
+    1.0 on keyOn and to 0.0 on keyOff.
+
+    by Perry R. Cook and Gary P. Scavone, 1995 - 2004.
+*/
+/***************************************************/
+
+#include "Asymp.h"
+#include <math.h>
+
+Asymp :: Asymp(void) : Envelope()
+{
+  factor_ = exp( -1.0 / ( 0.3 * Stk::sampleRate() ) );
+  constant_ = 0.0;
+}
+
+Asymp :: ~Asymp(void)
+{    
+}
+
+void Asymp :: keyOn(void)
+{
+  Envelope::keyOn();
+  constant_ = ( 1.0 - factor_ ) * target_;
+}
+
+void Asymp :: keyOff(void)
+{
+  Envelope::keyOff();
+  constant_ = ( 1.0 - factor_ ) * target_;
+}
+
+void Asymp :: setTau(StkFloat tau)
+{
+ if (tau <= 0.0) {
+    errorString_ << "Asymp::setTau: negative or zero tau not allowed ... ignoring!";
+    handleError( StkError::WARNING );
+    return;
+  }
+
+  factor_ = exp( -1.0 / ( tau * Stk::sampleRate() ) );
+  constant_ = ( 1.0 - factor_ ) * target_;
+}
+
+void Asymp :: setTime(StkFloat time)
+{
+  if (time <= 0.0) {
+    errorString_ << "Asymp::setTime: negative or zero times not allowed ... ignoring!";
+    handleError( StkError::WARNING );
+    return;
+  }
+
+  StkFloat tau = -time / log( TARGET_THRESHOLD );
+  factor_ = exp( -1.0 / ( tau * Stk::sampleRate() ) );
+  constant_ = ( 1.0 - factor_ ) * target_;
+}
+
+void Asymp :: setTarget(StkFloat target)
+{
+  Envelope::setTarget( target );
+  constant_ = ( 1.0 - factor_ ) * target_;
+}
+
+StkFloat Asymp :: tick(void)
+{
+  if (state_) {
+
+    value_ = factor_ * value_ + constant_;
+
+    // Check threshold.
+    if ( target_ > value_ ) {
+      if ( target_ - value_ <= TARGET_THRESHOLD ) {
+        value_ = target_;
+        state_ = 0;
+      }
+    }
+    else {
+      if ( value_ - target_ <= TARGET_THRESHOLD ) {
+        value_ = target_;
+        state_ = 0;
+      }
+    }
+  }
+
+  lastOutput_ = value_;
+  return value_;
+}
+
+StkFloat *Asymp :: tick(StkFloat *vector, unsigned int vectorSize)
+{
+  return Generator::tick( vector, vectorSize );
+}
+
+StkFrames& Asymp :: tick( StkFrames& frames, unsigned int channel )
+{
+  return Generator::tick( frames, channel );
+}